近日，國(guó)際著名雜志《細(xì)菌學(xué)雜志》Journal of Bacteriology上刊登了美國(guó)及泰國(guó)研究人員的最新研究成果“Pseudomonas aeruginosa thiol peroxidase protects against hydrogen peroxide toxicity and displays atypical patterns of gene regulation”，文章中，研究者揭示了綠膿桿菌巰基過(guò)氧化氫酶不僅可以免于過(guò)氧化氫的毒性，而且可以以非對(duì)稱的方式來(lái)調(diào)節(jié)基因的表達(dá)。
巰基過(guò)氧化氫酶（Tpx）以前被認(rèn)為是一種清除酶，而且Tpx是許多原核生物過(guò)氧化物酶基因家族的成員之一,，Tpx包括了巰基依賴的過(guò)氧化氫酶活性，而且可以通過(guò)減少硫氧還蛋白Trx來(lái)降低有機(jī)的過(guò)氧化物或者過(guò)氧化氫,。
銅綠假單胞菌俗稱綠膿桿菌,，是一種革蘭氏陰性菌，可以引起院內(nèi)急慢性感染,。細(xì)菌在環(huán)境中必須面對(duì)吞噬溶酶體產(chǎn)生的活性氧,，包括超氧負(fù)離子、過(guò)氧化氫和過(guò)氧亞硝酸鹽,。綠膿桿菌擁有多種策略來(lái)對(duì)克服環(huán)境中的有毒物質(zhì),，一些活性氧清除酶在氧化應(yīng)激性保護(hù)方面扮演著重要的生理作用。而且綠膿桿菌還可以產(chǎn)生超氧化物歧化酶來(lái)歧化超氧負(fù)離子,，解除過(guò)氧化氫的毒力作用,。
在文章中，研究者揭示了綠膿桿菌細(xì)胞質(zhì)中的抗氧化酶Tpx具有巰基依賴的過(guò)氧化氫酶活性,，而且對(duì)于有機(jī)過(guò)氧化物具有高效的親和力,。對(duì)tpx突變體的表型分析,，研究者揭示了其突變體對(duì)于不同濃度過(guò)氧化氫的敏感性表型,，突變體對(duì)于亞毫克濃度的過(guò)氧化氫的敏感性是在Tpx對(duì)于過(guò)氧化氫一定的Km之內(nèi)的，就好比是Tpx在亞毫克級(jí)別為細(xì)菌提供了一套防御機(jī)制,。研究者最后表示,，基于對(duì)秀麗隱桿線蟲的實(shí)驗(yàn)發(fā)現(xiàn)Tpx對(duì)于綠膿桿菌的毒力沒有影響。（生物谷Bioon.com）
編譯者：T.Shen
doi:10.1128/JB.00347-12
PMC:
PMID:
Pseudomonas aeruginosa thiol peroxidase protects against hydrogen peroxide toxicity and displays atypical patterns of gene regulation
Nawarat Somprasong1,2, Thichakorn Jittawuttipoka2, Jintana Duang-nkern1, Adisak Romsang2, Pimchai Chaiyen3, Herbert P. Schweizer5, Paiboon Vattanaviboon1 and Skorn Mongkolsuk1,2,4,6,*
The Pseudomonas aeruginosa PAO1 thiol peroxidase homolog (Tpx) belongs to a family of enzymes implicated in the removal of toxic peroxides. We have shown the expression of tpx to be highly inducible with redox cycling/superoxide generators and diamide and weakly inducible with organic hydroperoxides and hydrogen peroxide (H2O2). The PAO1 tpx pattern is unlike the patterns for other peroxide scavenging genes in P. aeruginosa. Analysis of the tpx promoter reveals the presence of a putative IscR binding site located near the promoter. The tpx expression profiles in PAO1 and the iscR mutant together with results from gel mobility shift assay showing that purified IscR specifically binds the tpx promoter support the role of IscR as a transcriptional repressor of tpx that also regulates the oxidant-inducible expression of the gene. Recombinant Tpx has been purified and biochemically characterized. The enzyme catalyzes thioredoxin-dependent peroxidation and can utilize organic hydroperoxides and H2O2 as substrates. The Δtpx mutant demonstrates differential sensitivity to H2O2 only at moderate concentrations (0.5 mM) and not at high (20 mM) concentrations, suggesting a novel protective role of tpx against H2O2 in P. aeruginosa. Altogether, P. aeruginosa tpx is a novel member of the IscR regulon and plays a primary role in protecting the bacteria from sub-millimolar concentrations of H2O2.
